Okay so you have replaced one wylex MCB with another - the new NHX are ugly but it should fit okay.
If the MCB fails to latch and you are sure you have wired it correctly in the Consumer Unit then you are going to have to start looking at switches and ceiling roses.
If all the switches are off and it wont latch then the problem could be a loose or burnt wire in the ceiling roses live and neutral loops or the switch wire. There could also be a loose wire at the switch itself.
If you understand how to and you have a multimeter available you could do a test for continuity - most diy multimeters don't have the ability to do the other test - insulation resistance.
As a start make sure the circuit is dead and then examine the conductors at each of the switches and ceiling roses - see if any are loose or burnt out.
If you have downlights in the bathroom or kitchen (steam) and they are not IP rated then make sure no copper is visible.
Good luck.
If the MCB fails to latch and you are sure you have wired it correctly in the Consumer Unit then you are going to have to start looking at switches and ceiling roses.
If all the switches are off and it wont latch then the problem could be a loose or burnt wire in the ceiling roses live and neutral loops or the switch wire. There could also be a loose wire at the switch itself.
If you understand how to and you have a multimeter available you could do a test for continuity - most diy multimeters don't have the ability to do the other test - insulation resistance.
As a start make sure the circuit is dead and then examine the conductors at each of the switches and ceiling roses - see if any are loose or burnt out.
If you have downlights in the bathroom or kitchen (steam) and they are not IP rated then make sure no copper is visible.
Good luck.
